Drill out the bolt hole

A 4mm drill will have to go through the entire wrist. Metric bolts are made just smaller than the hole they are intended to go through so a M4 bolt will be a perfect fit inside a 4mm hole. A metal collar is used to hold the cut open and prevent the drill bit from tearing up the skin. After drilling all the shavings need to be removed and this will take some time. Be thorough, and take your time. If you know a dentist do this at his surgery so that you can vacuum out the shavings.